The present invention relates to collators, and particularly to collators operable to stitch groups of sheets containing a selected number of sheets and to reject groups of sheets containing more or less than the selected number of sheets.
A known collator includes a plurality of hoppers which are disposed in a linear array along a main conveyor assembly. The main conveyor assembly sequentially moves groups of sheets received from the hoppers to a transfer station where the groups of sheets are sequentially engaged by a shuttle assembly. The shuttle assembly moves each group of sheets in turn to a stitching station where the group of sheets is either saddle, side or corner stitched. Each group of sheets is then moved from the stitching station through a folding station. After a group of sheets is folded, it moves to an upper discharge station. If a group of sheets is not to be folded, it passes to a lower discharge station. This known machine is disclosed in U.S. Pat. No. 3,554,531.
The machine shown in U.S. Pat. No. 3,554,531 has been improved by using a conveyor belt assembly to move groups of sheets to and from a stitching station. The conveyor belt assembly has upper and lower runs which grip the groups of sheets. This structure is disclosed in pending U.S. patent application Ser. No. 234,923, now U.S. Pat. No. 4,386,768 filed Feb. 17, 1981 by Victor A. Zugel and entitled "Signature Feeding And Stitching Method And Apparatus".
The machines shown in U.S. Pat. No. 3,554,531 and in pending application Ser. No. 234,923, now U.S. Pat. No. 4,386,768 when built and sold commercially incorporated a mechanism for sensing if a particular group of sheets contained more or less than a selected number of sheets. If a particular group of sheets was defective, i.e., included more or less than the selected number, the machine would stop to allow the defective group to be removed from the machine. This results in slowing the output of the machine.
Also, when the existing machines are being set up for a given job, such as adjustments being made to the hoppers, groups of sheets would travel completely through the machine. The sheets of such groups generally end up as waste, since the sheets are distorted or otherwise damaged due to their passing through the machine.